1. Field of the Invention
The present invention relates to an information distribution system such as a video-on-demand (VOD) system providing information services to a plurality of subscribers. More particularly, the present invention relates to a method for reducing the latency experienced by system subscribers transitioning between offered information services within such a system while maintaining high quality presentation of subscriber requested information services.
2. Description of the Background Art
In an information distribution system, such as video on demand (VOD) system, an information provider (e.g., a head-end in a cable television system) must control of the distribution of requested information to ensure that requests for information, such as video information, are satisfied in an orderly manner.
Compression and decompression techniques utilized within such systems to efficiently store and provide content to system customers (e.g., users or subscribers within a VOD system), as well as processing of control information provided by such customers requires a substantial amount of time. As such, a customer may experiences a significant delay or latency between the time a function is selected (via a set top terminal or set top box associated with the customer) and the time that the selected function is actually implemented upon the screen of their television. Heretofore this latency has merely been an annoyance which, for the most part, has been ignored by the interactive information distribution system providers.
Typically, upon selection of a certain function, such as stop or pause, while viewing a particular video stream, the present VOD systems merely delay the time of implementing that stop or pause function by the amount of latency, which can be in excess of five seconds. Furthermore, if a customer has a particular video stream being displayed and then selects a second video stream for display, present systems, after a slight control signal processing delay, switch from one video stream to another video stream without any attempt to smooth the transition. As such, the video that is received and decoded by the user's set top terminal is generally garbled or distorted during the transition period. If a customer is rapidly switching from video stream to video stream, e.g., channel surfing, the customer will view garbled video images for a substantial amount of time between “channel” changes. Such an extended period of garbled images is unacceptable for a commercial system.
A method and apparatus for masking the effects of latency within an interactive information distribution system is described in U.S. Pat. No. 5,781,227, issued Jul. 14, 1998 and assigned to DIVA Systems Corporation of Redwood City, Calif. The '227 patent utilizes, inter alia, video and audio masking techniques at the set top terminal to mask latency inherent in transitioning between information streams.
Unfortunately, the '227 patent masks latency without addressing contributions to system latency caused by information server processing of subscriber requests. Therefore, there is a need in the art for a method and apparatus for avoiding the effects of latency in an interactive information distribution system. More specifically, there is a need for a method and apparatus for reducing latency caused by information server processing of subscriber requests.